Graphic machine



P. GRAHAM GRAPHIC MACHINE Feb. 4, 1964 3 Sheets-Sheet 1 Filed April 16, 1959 FlGJA FIGJB FIG.|C F|G.|D FIG.|E FIG.IF

uvvszvroa Phi/lip Graham Feb. 4, 1964 P. GRAHAM 3,120,060

GRAPHIC MACHINE 3 Sheets-Sheet 2 Filed April 16, 1959 IIII'II INVENTOR.

49 Lg 0 Hk BY Phi/lip Graham %%-i 4 Affarney Feb. 4, 1964 P. GRAHAM 3,120,060

I GRAPHIC MACHINE Filed April 16, 1959 3 Sheets-Sheet 5 FIG."

FIG. l4

INVENTOR.

" Phi/lip Graham I ll 1 Affarney United States Patent M 3,120,060 GRAPHIC MACHINE Phillip Graham, 2825 Gleumore Ave., Pittsburgh, Pa. Filed Apr. 16, 1959, Ser. No. 806,963 13 Claims. (Cl. 33'76) This invention relates to a graphic machine which is useful, in general, as a guide for aiding in engineering drawing work, template making, sheet metal fabricating layout work, and the like, so as to quickly and accurately measure and draw straight lines at various pitches or slopes. This application is a continuation-in-part of my co-pending application, Serial No. 364,674, filed June 29, 1953, now Patent No. 2,882,604, entitled Graphic Machine.

The graphic device of the present invention differs from the graphic machine described in my co-pending application by having a carriage mounted on the square, the carriage having a marking means and a scaling means en gaged on it, the marking means allowing the operator to draw sketches with uniform selective width lines with ease. Furthermore, the present invention has an improved index arm, a larger more useful protractor andv improved edge scales.

An object of the present invention is to provide an L- shaped square graphic machine having a novel index arm mounted to allow unobstructed drawing action along the adjacent edge of the L-shaped square.

Another object of my invention is to provide a graphic device which is readily attachable to a conventional drafting machine so as to enable the machine to he used to selectively measure and draw more rapidly and accurately.

A still further object of my invention is to provide a novel graphic machine having an index arm with improved adjustable pin positioning means that is simpler to operate, simpler and less costly to manufacture and less cumbersome.

A still further object of the invention is to provide a novel L-shaped square type of graphic machine having a carriage mounted on it. The carriage has a marker and scale engaged to it. The carriage is free to move along the legs of the square and to move from one leg to the other to allow easier drawing and scaling of sketch lines at right angles to each other.

Other objects and advantages of my invention will become more apparent from a study of the following description taken with the accompanying drawings wherein:

FIGURE 1A is a fragmentary plan view of a drawing board with the graphic machine embodying the principles of this invention, positioned thereon in one of its many working positions;

FIGURES 1B to IE, inclusive, show fragmentary plan views of a drawing board with the graphic machine illustrated in some of the possible positions other than that shown in FIG. 1A;

FIGURE 2 is an enlarged fragmentary plan view with the graphic machine positioned the same as in FIG. 1A showing in detail some of the principles of the graphic machine embodied in this invention;

FIGURE 3 is an enlarged fragmentary sectional elevation taken along line 33 of FIG. 2;

FIGURE 4 is an enlarged fragmentary sectional elevation taken along line 44 of FIG. 2;

3,120,060 Patented Feb. 4, 1964 FIGURE 5 is a fragmentary sectional elevation taken along line 55 of FIG. 2; 7

FIGURE 6 is an enlarged fragmentary sectional elevation taken along line 66 of FIG. 2;

FIGURE 7 is an enlarged fragmentary sectional elevation showing a modified transparent edge scale and its relationship to the edge of the square;

FIGURE 8 is an enlarged fragmentary plan view taken along line 88 of FIG. 5;

FIGURE 9 is a sectional elevation taken along line 99 of FIG. 8;

FIGURE 10 is a fragmentary sectional elevation taken along line Ill-10 of FIG. 8;

FIGURE 11 is a fragmentary sectional elevation taken along line 11-11 of FIG. 8;

FIGURE 12 is an enlarged detail of a typical nut used to position the pin holders on the index arm;

FIGURE 13 is a fragmentary sectional plan view taken along line 13-13 of FIG. 10;

FIGURE 14 is a plan View showing a modified method of using this graphic machine by suspending it from a swiveled arm;

FIGURE 15 is a plan view showing a modification of the graphic machine used in conjunction with parts of a conventional drafting machine;

FIGURE 16 is a plan view showing a further modification of the graphic machine used in conjunction with a conventional drafting machine;

FIGURE 17 is a plan view showing a modification of the graphic machine, using conventional drafting machine scales in the construction.

Referring more particularly to FIG. 1A, the drawing board 1 has a T-square straight edge 2 on top of it. A conventional so called parallel straight edge may be used in place of the T-square. The board 1 may have a slot along the left hand side which forms a track for a removable pin in the T-square 2. This slot and pin arrangement restrains the T-square from moving out of alignment. The square or L-shaped square Q, which embodies many of the principles that are new and useful, is shown attached to the T-square 2. The L-shaped square Q is generally referred to as a square since that is the term used to designate similar types of squares. A carriage B is engaged to the L-shaped track on the square Q. The operator may rest his hand on the carriage B as he grips a pen or pencil and draws. The operator may draw along the edges of the square Q without using a carriage B. The square Q is shown tilted, as it can be selectively tilted to enable an engineering draftsman, template maker, or the like, to readily draw sloping lines. The tower structure sketch 3 can be drawn quickly with the aid of the square Q. When the operator uses the carriage B, as it is shown mounted on the square, he draws along the inside edges of the square Q. This arrangement allows the operator to draw two lines at right angles to each other to form a corner without moving the square Q. If the operator prefers to draw with a carriage along the outside edges of the square Q, he may use a modified carriage B that allows the marker and scale on the carriage to be raised to clear the offsets on the ends and center of the outside of the square Q. The carriage would be turned one hundred and eighty degrees for use on the outside of the square. A square Q may have a carriage such as carriage B mounted on each leg, which would be a particular advantage if he intends to draw only on the outside edges of the square Q.

A small square Q, without a carriage, would be highly useful when used with common pencils and pens, the lines being drawn along both the inner and outer edges.

FIGS. 1B, 1C, 1D, 1E and 1F show the square Q in some other tilted and non-tilted positions that may be used to aid in drawing the sketch 3. The square Q may be inverted and be used against the opposite or near edge of the T-square 2 if the draftsman prefers such an arrangement. As can be seen in the enlarged plan view FIG. 2 which. is similar to FIG. 1A, the sketch 3 is a line diagram of a tower structure, which is a typical elevational view for structural steel plans. The left and right hand tower legs have the same slope. The slope is also called the angle, bevel, or pitch, in structural drawing Work. The towersketch 3 is, in general, symmetrical about its center except for the splices of the three tiers of bracing and.

the dimension lines,.which are given on one leg only, for example. The sketch 3 has various length lines at various slopes. They are the horizontal and vertical lines, three sets of diagonal bracing lines having different bevels orslopes, and the tower legs which have another slope. All the slopes are both right and left hand. When the engineering draftsman makes shop detail drawings of such a steel tower, he must draw hundreds of structure lines, dimension lines, extension lines, and guide lines for lettering, etc., in these various slopes. A large tower may require many drawings, 24 inches by 36 inches, usually drawn to one inch scale equalling one foot; so, by using the squareQ to aid in accurately and speedily measuring and drawing these lines, accurate work on large jobs can be made quickly at low cost. The draftsman has to draw a' little bit here and there to create a shop detail sketch, etc., thus this type of drawing work has a sequence which causes frequent changing of drawing procedure from one set of angles to another, as well as horizontal. 1 and vertical.

The square Q has an index arm N1 which is used to holdselective units with pins for tilting the square Q. This arrangement allows the operator to set-up this square Q for obtaining and maintainingall the angles, or slopes that are to be used for drawing the tower sketch 3. Once the squareQ is set-up, there are simple operations to be made by the workman to change to the position back and forth for various sets of angles and to the horizontal and vertical positions, as will be'described fully further on.

The square Q hasa body or frame 4. The frame 4 has legs 4d and 4e, also pin arms 4a, 4b, and 4c which have holes to take pinsSa, 5c, and 5d. These pins may be similar to the pin 5b. The pins are positioned so they may be made to bear against the edge of the T-square 2 to adjust the square Q to various tilting positions; the pins are also a means used to pivot or rock the square Q to various positions. The. pins 5a, 5b, 5c, and 5d form bearing points thatcan selectively bear against the edge of the T-square 2. Normally, the pins 5a, 50, and 5d. are inserted fully, like thepin 5c is positioned as shown in FIG. 4 and allowedto remain in that position. The pins may be raised to positions like the position 5ca, shown in FIG. 4 to allow disengaging of protractor-clamps from the square Q.

The protractor-clamps C1, C2, C3, and C4, which are alike, are engaged by the pins 5a, 5b, 5c, and 5d. The clamps C1, C2, C3 and C4 are selectively coupled to the T-square straightedge' 2 to restrain the square Q from tilting out of selective tilted and non-tilted positions. Thesesprotractor=clamps are slidable along the straight edge orT-square-l even when they are clamped to it. These clamps may be omitted when the device is to be used to a limited degree, or they'may be disengaged when they are'not requiredfor a given sketching operation. A typical clamp Clis shown in enlarged elevation FIG. 4; it is a self-aligning and self-coupling clamp; the clamps will be described in detail further on.

The pins 5a, 50, and 5d may be fixed permanently to the arms on the frame 4, and to the clamps C1, C2, and C4, if such an arrangement is preferred.

When for limited operations none of the protractorclamps C1, C2, and C4 are to be used, pins 5a, 5c, and 5d may be used without the clamps, or the pins may be omitted; and the outside corners of the frame 4 may be used as the bearing points, or the square Q may have the magnetic clamps 29a, 29b, and 29c embedded in the frame 4 to act as the outside corners, the magnetic clamps acting as hearing points and clamps. The magnetic clamps are pieces of magnetized metal such as alnico. The magnetic clamps may be used to hold the square Q to the T-square 2. The edge of the T-square 2 would have a strip of iron 30 to work with the magnetic clamps. When the magnetic clamps are brought close to the strip of iron 30, magnetic attraction causes the clamps to bear and hold tightly against the strip 39. These magnetic clamps prevent the square Q. from pulling away from the straight edge, while they allow it to he slid along the edge. The magnetic clamps 20a, 29b and 290 are offset from the edges 4g to form projections. When. the pins 5a, 5a, and 5d are omitted, two of these projections along one of the edges 4g engage the edge of the T-square 2 to space theadjacent edge 4g away from the T-square when the square Q is positioned against the T-square in parallel relationship, such positioning provides a gap between the edge of the T-square and the adjacent edge 4g to allow the draftsman to scale and draw within the gap along the adjacent edge 4g. When the pins 5a, 50, and 5d are used, they act as projections instead of the clamps 29a, 29b, and 290 acting.

The pins may all be alike so as to be interchangeable. The pins are threaded almost their full length for engaging the pin arms and the pin holders H1, etc. The pin ends engage plain close fitting holes in the protractorclamps C1, etc. The pins may be bowed slightly when made of resilient material so they will fit tightly in pin arms. The pins may also be magnetized to bind them to engaging parts of iron, the pins may then actas magnetized' clamps. A resilient wire 25 extends through clamp C1,,as shown in FIG. 4. This wire 25 springs aside into a suitable groove in the protractor-clamp when a pin is inserted or removed. This wire 25 acts as a key to fit in the keyway-like groove near the bottom of the pin, to hold the pin and the protractor-clamp together. The clamps C1, C2, C3, and C4 and the arms 4a, 4b, and 40 may have hardened sleeve inserts for preventing wear and tear from the pin action.

The T-square 2 may be used as T-squares are normally used, that is, it may be pushed up and down the drawing board 1 and the square Q may be kept against the T- square and he slid with it and then along its length. The square Q may also be disengaged from the T-square 2 and be moved independently to a desired position along the T-square. The ends of the frame legs 4d and 4e are beveled at about 45 degrees so that the square Q may be tilted to 45 degrees in arrangements similar to that shown in FIGS. 18 and 1E.

As shown in FIG. 3, the transparent frame edgings 411 and 4g are beveled on the top to allow a suitable working edge for drawing. A fragment of. a conventional pencil 6 is shown by a dot-dash outline. The operator may draw with a pencil 6 as shown in FIG. 3, or he may draw with a marker engaged to the carriage B. The frame 4 may be made of lightweight suitable materials such as plastic or aluminum. It is highly desirable to have transparent working edgings 4h, 4k, and 4g, so that the draftsman may see how close he is drawing to adjacent lines that are below the edgings. If the frame 4 is to be made of clear plastic, frame 4 and edgings 4h, 4k, and 4g may be combined and be made of one piece.

The inside edge of the square Q has the scale assemblies S1 and S2; assembly S1 is shown below the outside edging 411 in FIG. 3'. The edgings 4g may havescales S3 which may be like scale S1. The scales may be of transparent plastic. The edgings are shown recessed to receive the scales. The recesses provide protection to prevent damage to the scales, and the recesses would keep the scales in alignment. If the frame 4 and the edgings are made of aluminum or other opaque materials, the scales may be located on the top of the edgings in the position 811a, shown above edging 4h by a dot-dash outline in FIG. 3. When the square Q is to be used only with one set of scales, such as full size scales for template making and shop work, the scales may be marked on the top of opaque frames or edgings. Such full size scales may be marked on the bottom or the top of a transparent frame edge. An opaque frame with opaque edgings may be modified from that section shown in FIG. 3 so as to allow the transparent scales to project out further from the frame edgings 4h, 4k, and 4g. As can be seen in FIG. 3, the scale assembly S1 has a roughened reinforcement wire 26 at its center. As the plastic scale 27 would likely have a high coefiicient of expansion, the wire 26, with a low coeificient of expansion, is used to restrain the plastic from expanding or contracting excessively in length. Thus the reinforced scale does not cause inaccuracies in measuring. The wire 26 may be sandwiched between two pieces of plastic that are fastened together to form the base of the scale, or a single strip of plastic 27 may be used with the reinforcing wire 26 imbedded in it. The scale markings may be made with a photographic process. The photographic reproduced markings may be made at low cost in suitable colors or in black and white. Scales may have their graduation markings numbered from left to right in one color and from right to left in another color, so as to allow the operator to scale in either direction with little chance for errors. Small balls 26b and 26c are attached to the ends of the wires 26 so that the scales S1 and the like may be detached or attached quickly and accurately to the square Q. These balls 26b would fit into suitable sockets cast into the frame or edging at the center. The sockets are slightly smaller in diameter than the balls Ztib and 260, since such transparent plastic edging as edge 411 is slightly resilient and the balls can be forced into the sockets with slight hand pressure. The scale assemblies S1 and the like may be quickly removed from the edge 4k and the like, by prying it loose with a ruling pen blade, by making several insertions and twists with the blade. Each wire 26, at the outer ends of the scales, has a spring 26d which keep the scales taut. The scales S1, and the like, may be made so their gradnations start at zero, where they meet at the center of the square Q, and graduate out to their ends, so that measurements may be taken in two directions from the center from one position of the square Q. Conventional interchangeable drafting machine scales require a second positioning for scaling at a right angle to the first operation. In general, the scale assemblies S1 and the like would be interchangeable with scales of other graduations. These scale assemblies are shown as having graduations on two edges so as to combine two different scales that are frequently used in one assembly, so they will be readily available when needed. They may be turned over quickly by unhooking the one end, flopping and rehooking the ball ends to change from one desired scale to another.

Conventional interchangeable drafting machine scales have tight fitting tapered sockets which make scale changes a tedious, less accurate, and longer operation. Frequent changing of the scales is often required, since the scale edges in working position may, for instance, be of one inch equals one foot; and it becomes necessary to frequently replace them with scales of 3 inches to a foot for making enlarged details or large layouts, before resuming with the detail sketching at one inch scale. A set of scales S3 in different scale registry from that on the scales S1 and S2 would be useful at times when a sketch, for instance, is drawn with a small scale for overall sizes and a larger scale for the details.

'FIGURE 7 shows a modified scale assembly S4. The plastic scale 27a is cemented to the metal strip 26a. Two or more dowels 262 in the strip 26a are pressed into holes in the edging 411 and the like. Dowels 26c engage dowel holes in the transparent working edge ill and the like. The holes are slightly smaller in diameter than the dowels 26c, since such transparent plastic as edge 4h is slightly resilient and the dowel can be forced into the holes with slight hand pressure. The scale assembly S4 may be quickly removed from the transparent edge 4h by prying it loose with a ruling pen blade, by making several insertions and twists with the blade. The metal strip 26a takes the friction forces and protects the scale 27a. Only one edge of the scale 27a is marked with the arrangement shown. A modified scale (not shown) may have the strip 26a centered, the scale having markings along each edge.

The pin 5b is held in the pin holder H1 (see FIGS. 2 and 5), which is attached to the index arm N1 (see FIGS. 2 and 5). There is a means to accurately set the pin holder H1 so as to create an indexed location to aid in quickly and accurately obtaining the desired tilted position for the square Q for a drawing operation at an angle or slope. This will be described in detail further on. Other identical pin holders H2, H3, and H4 are shown. They are all attached and selectively positioned to the index arm N]. for the various slopes or angles required for drawing the sketch 3. The pin 511 projects down, as does the pin 5c, so that it can be made to bear against the edge of the T-squrare, 2. The pin 5b is located at a position which is equidistant from the pins 5a and 50. With the pin 5c and the pin 5b bearing against the T- square 2, as shown in FIG. 2, an angle or bevel is created between the T-square 2 and the bottom'leg of the square Q. This tilt of the square Q creates the proper slopes for measuring and drawing the left hand leg of the tower shown in the sketch 3. The tower leg is drawn along the leg 4d of the square Q. The leg 4c of the square is sloped at an angle complementary to the angle created by the leg 4d. This sloping leg 4e is used in the drawing of the extension lines out from the left hand tower leg, :so they suit the dimension lines that are drawn parallel with the tower leg. After the left hand leg of the tower in the sketch 3 is drawn, or partially drawn, the square Q may be pivoted or rocked on pin 5b until pin 5a bears against the T-square 2. This position is shown in FIG. 113. It creates the same degree angles that were created in the arrangements shown in FIGS. 1A and 2, except that they are opposite hand or reversed in respect to the legs of the square Q. With the set-up shown in FIG. 1B, the right hand leg of the tower can be measured and drawn along the leg 4d of the square; and any dimension lines can also be drawn along the leg 4d, with extension lines or dimension lines being drawn at right angles with the leg 42 of the square. Thus it can be seen that with the pin 51) indexed in index arm N1, the draftsman can draw these two sets of slopes by quickly changing back and forth from one set of complementary slopes to another merely by rocking the square Q with the pin 5!) bearing against the T-square 2.

When the draftsman Wants to draw the horizontal and vertical lines in the tower in the sketch 3, the pin 5b may be removed or raised so that it no longer engages the protractor-clarnp C3 and the T-square 2; or the index arm N1 may be removed temporarily if desirable, particularly while consecutively drawing a great many horizontal and vertical lines. The square Q is positioned as shown in FIG. 1C by rocking or pivoting it until the pins 5a and 50 both bear against the T-square 2. Then the horizontal lines can be measured and drawn along the leg 46, and vertical lines can be measured and drawn along the leg 4d. The position of the square Q, as shown in FIG. 1C, is considered to be the most desirable arrangement for-drawing vertical and horizontal lines by a right handed draftsman. Since the square Q is used to measure and draw, it is highly desirable at times to pivot the square Q to the position shown in FIG. 1D, with the pins c and Szl bearing against the T-square 2. With this arrangement, the draftsman may measure and draw the vertical and horizontal lines from a common point when it is more suitable for the sketching being done. Thus it will be seen that even a right handed draftsman will use the square Q in the position. shown in FIG. 1D to allow him to draw andscale at the same time. A left handed draftsman would find the positions of the square Q as shown in FIGS. l-D, 1E, and IF highly desirable for his technique.

To use the square Q in the positions shown in FIGS. 1E and-1F, the index arm N1 is unhooked from the frame leg 40, where it is hinged, and is moved to the position shown by a dot-dash index arm outline N2 on the leg 4d. The square Q is tilted as shown in FIG. 1E, by having the pins 51'; and 5d bear against the T-square 2. The draftsman, whether he is left or right handed, takes his choice whether he wants to use the square Q in positions such as that shown in FIGS. 1A and 1B or in the positions shown in FIGS. 1E and IF. All draftsmen would, at times, switch the index arm N1 to give the alternate arrangement when conditions would require it, such as when he is sketching near the ends of the T- square 2. The pin holders H1, etc., can be indexed in the index arm N1- to give up to a 45 degree tilt for the flat angles to the horizontal, which is all that is necessary, since the complementary angles on the other leg of the square give the steep angles to the horizontal, from 45 degrees to 90 degrees. The pins and straight edge means or the like that maintains the square Q into a set position as it is swept over a drawing is defined as an angular positioning means since it can be used to set the square at any angle from ninety degrees or zero degrees to fortyfive degrees.

Another index arm, identical to the index arm N1, may be used in the position N2. Either one or both of them may be attached at the same time, if so desired. In general, one would be removed to keep down the weight and to make the device noncumbersome.

When the draftsman wants to draw the top set of bracing of the tower in the sketch 3, he removes the pin 5b from the pin. holder H1, and inserts it in the pin holder H2, which has or is adjusted to give the proper angle or tilt. With this tilt, one diagonal brace and the dimension lines for it may be drawn against the leg 4e of the square Q; and the lines drawn to complementary slopes or angles would be drawn against the leg 4d of the square. After this operation, the square Q is rocked or pivoted on the pin 5b against the T-square 2, to the opposite position. This would allow the other top diagonal brace in the tower to be drawn. After the top set of bracing has been drawn, or partially drawn, on the tower 3, the pin 5b is removed from the holder H2 and inserted into the holder H3 until it projects far enough to allow it to bear against the T-square 2, then the middle set of diagonal bracing may be drawn or parts of it may be drawn. Then the pin 5b may be removed and inserted into the holder H4, so it can be made to bear against theT-square 2. Thus the square Q can be tilted to enable the draftsman to draw the lower set of the bracing on the tower 3.

Although I have referred to the pin 5b as being removed from the pin holder H1 and inserted in other pin holders, pins identical to the pin 51) may be inserted in the pin holders H2, H3, and H4 to make them quickly available. When not being used, these pins would be kept in a raised position, such as that which is shown by a dot-dash pin outline above the pin 5b in FIG. 5. They are raised enough to prevent them from engaging the protractor-clamp C3 or from hearin against the edge of the T-square 2. If a tower similar to that shown in the tower sketch 3 were to have more diagonal members, or details 8; of diagonal connections to adjoining parts, more pin holders, similar to the holder H1, may be fastened and posttioned to the index arm N1, or another such index arm, so as to provide all the required indexed angles. If so many indexed angles were required that they could not all be mounted on one or two index arms, additional index arms, similar to index arm N1, may be used for the.

over-flow. An index arm in position N2 may hold the additional. indexed angles.

The index arm N1 has a T-shape. The arm 9 is connected to the center of the beam 9a. The ends of the beam. 9a have hinged connections to the frame 4. The hinge sockets on the frame 4 are open at the top to allow the ends of the beam 9a to be engaged or disengaged from the frame.

The index arm N1 is inserted from a vertical plane to.

allow it to fit into the hinges, then it is pivoted down into a horizontal position, which locks it in place. The index arm N1 may be raised and lowered, by pivoting, to nearly a vertical position without unhinging. The hinges are so designed that they can take the thrust that is made against them by the pressure on the square Q by the draftsmans pencil. A raised position of the arm N1 is shown by the dot-dash outline in FIG. 5. The arm N1 may be pivoted to this raised position Nla to retract the pin 511 from its engagement with the edge of the T-square 2 while the square Q is being pivoted from a tilted position to a non-tilted position. When the arm N1 is to be pivoted to retract the pin 5b, the catch arm 13c may be locked into a raised position indicated by a fragmentary dot-dash outline.

The mounting of the index arm N1 allows the adjacent edging 4-g to be used fully for scaling and drawing with. a common pencil and the like, when the index arm is attached. The threaded arm 9 is rigidly joined to the beam 9a. The pin arms ta, 4b and 4c have hinge sockets to which the ends of the beam 9a are engageable. This offsetting of the index arm N1 creates a gap along the adjacent edge 4g, therefore allowing unobstructed drawing and sealing means along the edge 4g, which is an improvement over the mechanism of my Patent 2,882,- 604 that has direct mounting of the index arm that obstructs the adjacent. edge of the leg. A protractor 9c is attached to the arm 9 and the beam 9a. The protractor 9c may have degree graduations along one edge and bevelgraduations along the other edge. When the square Q is tilted, the degree of tilt is read against the edge of the T-square 2. The degree graduations may be numbered from zero at each end, to give the reading for the slope of each leg of the square Q. The large protractor al lows more accurate reading than can be made with the protractor clamps C1 and the like.

The arm 9 is threaded and slotted to allow the pin holder H1 and the like to be attached to it and be adjusted laterally along it. The pin holder H1 has a pin retainer 10, an adjusting nut 10a, an indicator 10b, and an elastic lock block 100. The retainer 10 is threaded to suit the pin 51). The indicator 10b is soldered to the retainer 10. The nut 10a is made in parts and hinged together as shown in FIG. 12. The retainer 10 is inserted in the slot in arm 9 at approximate position where the pin. 5b is to be positioned. The not 10a is opened and clamped around the arm 9 and the retainer 10, locking the retainer to the arm. The nut 10:: has a hook and notch engagement to lock the nut into a circle when the nut segments are pressed together. The nut 10a is made of spring steel or the like to allow its parts to be sprung. The pin 5b is inserted into the retainer 10. The nut 10a is rotated to obtain Vernier adjustment to position the retainer ltllaterally with respect to the adjacent edge 4g and thus selectively vary the distance between the adjacent edge 4g and the pin 51: to obtain selective tilting of the square Q. The retainer It: is grooved, but not threaded, to receive the nut 100, the groove and nut engage to lock the parts together. The indicator 10b has a needle pointer at each of its ends; the pointers register the tilt angle on the protractor-clamp C3. The small elastic block 100 is held by a recess in the bottom of the retainer 10. The elastic block 100 bears against a small area of the thread of the nut 10a, preventing the nut from creeping from vibration. A paper tab 10d may be attached to the indicator 10b with an adhesive. The tab ltld is useful to write the angular setting for the position of the pin holder H1. The nut 10a is turned by gripping it with the fingers. The pin holders H1, etc., are narrow to allow them to be set close together for indexing angles that are slightly different. The head of pin 55 is shown by a dot-dash outline in FIGS. 9 and 10 as FIG. 8 does not include the pin head. The pin b is inserted in the hole in the retainer after the pin holder H1 has been clamped to the arm 9. The pin 51) and the retainer 10 may be threaded steeply to allow the pin to be quickly advanced, to thus allow it to be quickly inserted or removed with little effort and without jarring or moving the square Q and the T-square 2 it may be clamped to.

The square Q may be lifted by gripping a threaded pin 5b, and in doing so the pin may be turned to advance it further so it will project to allow it to bear against the T-square 2, either with or without the protractor-clamp C3. The threaded pin 511 may be turned in the opposite direction to raise it so it will no longer project to engage the T-square 2 or the clamp C3. The threaded pins 5b, 5a, 50, and 5d are less likely to work loose it bowed slightly than would plain straight pins, especially when using the square Q with a sloping or vertically mounted drawing board 1. Threaded pins would allow one hand removal or insertion of the pins with little effort; this would be particularly useful to handicapped workmen with one useful hand.

The index arm may obviously be modified in many ways. The arrangement shown would be useful for a draftsman who details structural steel trusswcrk and the like. Other types of draftsmen would only need one pin holder. The pin holder may therefore be permanently engaged to the arm 9. The nut 10a may be made in one piece. The pin 5b may be non retractable from (the arm 9, the arm 9 being pivoted upwards to retract the pin 5b from engagement with the edge of the T-square 2,, or the arm 9 may be removed to retract the pin 5b.

The protractor-clamps C1, C2, C3, and C4 may be used when it is desirable; and they may be omit-ted o-r disengaged by removing or raising the pins 5b, etc., when they are not being used. Some types of dnafting work would not require the protractor-clamps C1, etc. Some types of work would not require the clamps but would make use of the p rotractors. The clamps may be used to securely hold the square Q in an inverted position to the lower edge of a T-square 2 or a cable rigged parallel edge, particularly so on a vertical or steeply sloped drawing board. The draftsman may raise the pins and slide the clamps aside until they are required again when the clamps are not useful for a panticular sketching operation. The clamps C1, C2, C3 and C4 hold the square Q to the T-square 2 when pressure on the edge of the square Q while drawing would have a tendency to tilt it. The clamps C1, C2, C3 and C4 are slidable along the T-square even when clamped to it. The protractor-clamp C3 is shown enlarged in FIG. 4; the other clamps may be identical or similar to it. The protnactor indicator needles 4 point to both the angles on the protractor for the set-up on the square, that is an angle and the complementary angle at right angles to it. Protractor part 13 of the protractor clamp C1, etc., may be made of such material as plastic or aluminum to keep the weight low; or they may be magnetized metal, such as aluminum-cobaltnickel, alloy such as sold under the trademark alnico, to hold it to an iron edged T-squ'are or other iron or steel edged guides. The protnactor part 13 has a hinged arrangement with a hinge part 1311, and a threaded catch arm 13c. The thread shaft of arm 13a is rectangular to 10 fit rectangular holes in hinge part 1317, so the arm cannot turn.

The effective length of the arm 130 is varied by the draftsman to allow the clamp to fit the width of his T-square 2. This adjustment is made by turning the threaded nut-like part 13g. The nut-like part 13g is tapped to suit the thread on arm 13c, it has spaced holes around its perimeter for attaching the lever-like handle I 13d. After the effective length of the arm 13c is adjusted to suit a particular T-square 2, the lever-like handle 13d is inserted in one of the spaced holes in part 13g. A thin resilient washer 13f around the arm 13c prevents the nut 13g from creeping. The handle 13d is pivoted from right to left to tighten the clamp C1 and it is pivoted from left to right to loosen the clamp C1 in its relation to the T-square 2 to adjust for play. The handle 13d is pivoted to the extreme tightening position when it is desirable to tighten the clamp C1 to the T-square 2 so it will not slide which is useful in keeping the square Q positioned for drawing vertical lines longer than the leg of the square. The hinge arrangement formed by the protractor l3 and the hinged part 131) has a machine screw Be. This machine screw 13c may be tightened with a screw driver when it is desirable to prevent any hinge action. As shown in FIG. 4, the non-threaded end of the arm is beveled. This allows the arm 130 to engage the T-square 2 and the loose hinge action allows the arm 130 to rise and slide over top of the T-square 2, and then to drop to engage T-square 2 securely as shown. When the arm 13a is to engage the T-square 2, after sliding over top of it, the weight of the arm 13c and a loose hinge arrangement will allow the arm 130 to drop, and the hook-like end of arm 130 will bear against the T-square 2, preventing the protractor-clamp Cl, etc., from disengaging in a lateral direction, thus locking the square Q in a position with the T-square 2, by means of this clamp or other combinations of the protractor-clamps C1, C2, C3, and C4. A slightly raised dot-dash outline of the arm 13c and the hinge part 13b, shown in FIG. 4, shows the elevated positions of these parts when they are sliding across the top of the T-square 2. The protractorclamps C1, etc., are self-aligning when they move against the edge of the T-square 2, unless they are over ninety degrees from their selected position. The arm 13c and the hinge part 13b together are raised up pivotally to slightly over ninety degrees to keep them disengaged from the T-square 2, when they are not wanted in play to clamp onto the T-square. This high raised position of the arm 13c and the hinged part 13b is shown by a dotdash outline in FIG. 4. To raise the arm 13c, the drafts man may insert his finger under the sloping end of the arm 13c and pull the arm 13c upwardly.

The index arm N1, as shown in FIG. 2, would at times prevent the full hinging action of the arm 13c and the hinge part 13b on clamp C3, as they would be blocked by the arm 9 and the pin holders. When that condition occurs, the pin 5b may be disengaged from the clamp C3 or the index arm N1 and the protractor-clamp C3 together. When this blocking condition occurs, the screw 132 may be tightened to prevent hinging action, and the arm N1 may be lifted, which will lift the clamp C3 also.

The raised strip 20 along the full length of the T-square 2, only a fragment is shown in FIG. 2, may be used on a T-square or straight edge, which is tapered in width or it is too wide to be practical for clamping across its width. The raised portion of a so called draftsmans parallel edge, that is a rigged straight edge with a system of pulleys and cables to keep it in alignment, may be clamped onto in place of a raised strip 20.

The clamp C4 may be disengaged and pushed aside when it is not being used, or the clamp C2 may be switched to the position of the clamp C4, if it is not being used on the arm 4a, thus eliminating a clamp. Thus, when the engineering draftsman wants to keep the weight of the square Q to the minimum, this switching I arrangement is used. If weight is no problem, or if it is preferred, a clamp C4 may be used while the clamp C2 is left on the arm 4a.

The carriage B may be used to measure and draw along the edges of the frame 4. The carriage B has a grooved base frame 11 which engages an L-shaped grooved track in the frame 4. The base 11 has a rigid protruding portion or offset 11m that protrudes laterally at an angle of forty-five degrees. A vertical shaft 11a slides and pivots in a hole in the protruding portion 11m. Control element or pivot arm 11b is supported by the shaft 11a. The pivot arm 11b supports a holder 110. The holder 110 may support a marker 11:1. The marker may be a pencil or the like. The marker 11d may have an elongated chisel point contact with the paper on the drawing board 1. Such a point may be made with a flat pencil lead, a rotating conical pencil point, broad contact ruling pens and the like. The control element 11b is gripped and pivoted to selectively pivot the marker 11d, so as to change the angularity between the elongated contact edge of the marker 11d and the longitudinal axis of the adjacent leg M or 4e. Varying the angularity varies the width of the marking path to be made by the elongated contact edge of the marker 110]. My patent No. 3,020,640, entitled Graphic Machine describes marking means that may be used to make selective width lines in response to selective pivoting of a pivot arm. The spring lle tends to raise the arm 11b and thus the marker lid. The arm 11b is selectively pivoted to positions that will cause selective width lines to be drawn. The arm 11!) is gripped by the operator from either side; the arm 11b is depressed so the marker 11d touches the drawing paper and the carriage B is pushed. The operators hand may rest on the base 11 while drawing. A ruling pen type marker may be fastened with the set screw 11 The arm 11b is selectively pivoted to a position for drawing a selective width line, then the arm 11]; is depressed. A chisel pointed offset 11g engages a groove of the gear-like index 111:, locking the arm 11b into the selected pivoted position. The index 1111 is soldered to the base 11, so it cannot rotate.

The base .11 may have a small L-shaped scale 11k attached to it, as shown in FIG. 2. The scale 11k is useful in drawing and scaling short lines. Such a scale may measure up to an inch from a starting point to the termination of a line. The operator may also use the scales along the edges of the frame 4 when drawing with the carriage B. The carriage B may be used without the marker 11d and the scale 11k, the carriage acting only as a means to support the operators hand, thus eliminating friction of the hand against the drawing and therefore preventing sores from the sliding action.

Thus there are many advantages to be had by using the L-shaped square Q rather than some conventional tiltable or protractor-like instruments of limited use, since with this device the draftsman, etc., can index for and maintain accurate groups of pairs of angles or slopes, and he can reciprocate, push, or place the square Q into position, where it is held by the T-square 2 to prevent it from tilting out of. the selective drawing position, and where he can measure and draw two lines at right angles to each other with one positioning.

In general with the present device, the draftsman can, by proper procedure in drawing, scale as he draws without taking more time than he would for unsealed drawing. The ease of positioning the square Q, the ease of maintaining a position, and the fewer positions required, are aids in maintaining speed and accuracy while drawing.

Drawing instruments other than the L-shaped squares, particularly edge guides, may be equipped with protractors and/or clamps such as clamp C1 or clamp 29a, index arms such as arm N1, and interchangeable scales such as scale assembly 51.

A U-shaped graphic guide device, similar to that formed by placing two squares Q toe to toe and fastening them together, may be made similar to square Q. It would be more cumbersome, but it does not require as much movement by the worker. It would be useful in some branches of drafting.

A full square shaped graphic guide device may be made similar to an L-shaped square with index arms, protractors, clamps, and interchangeable scales.

FIGURE 14 shows a modification similar to the arrangement shown in FIG. 1B. The square Q is clamped to the straight edge 2a, or other types of straight edges may be substituted. The square Q is supported by a swiveled arm 15, which is fastened to the board 1. This swiveled arm 15 is a triple hinged conventional device to support a load in various positions over a large area. The arm 15 is fastened to the ends of square Q. With this arrangement, the weight, or most of the weight, of the square Q may be carried by the arm 15; and thus it would take less effort for the workman to slide, rotate, or lift and move the square Q along the drawing surface. This arrangement may be used to lift the square Q slightly so that the operator could readily force the square to the working surface by slight pressure, or it may be adjusted to allow it to rest on the drawing while it is deflecting the arm 15 slightly with its weight, so little effort is required to lift it. The square Q is pivoted about a pin to get any of the desirable tilting positions that are required. This swiveled arm part attached to the square Q is shaped to counter-balance the square Q. The pivotable pin is at the center of gravity, so that the square Q remains at an approximate parallel plane from the working surface. The straight edge 2a is similar to the T-square 2. It has adjustable ends and a pin which projects into a metal grooved track near the left hand edge of the board 1. The straight edge 2a can be tilted to other than ninety degrees from the so called vertical edges of the board.

FIGURE 15 shows another modification using an L- shaped square that has index arms N3a and N3b. The square QR may have a carriage track and a carriage B. The index arm N3a is attached to an intermediate portion of the scaled leg 16b, like the index arm is connected to the square shown in my Patent No. 2,882,604. This arrangement allows the use of a lighter weight index arm. The arm N3a blocks the use of the adjacent edge of the leg 16b, but that edge is rarely used. Furthermore, the leg 16b is usually extra long and thus an index arm like arm N1 or index arm N312 would be cumbersome. The shorter leg 16:: has an arm N3b which is like index arm N1. The square QR is attached to a conventional drafting machine 16 in place of the pair of scaled legs that form an L-shaped square. The drafting machine 16 is a conventional device for measuring and drawing lines at various angles; it has a hinge which is connected to the drawing board 10. The portion of the hinge that is connected to the board 1a is so secured that it is prevented from moving or pivoting to thus anchor the machine 16. The drafting machine 16 is of the parallelogram type having a swivel arm that maintains the square QR in a selectively set tilted or non-tilted position with respect to the drawing board 1a, while allowing the square to sweep over the entire drawing surface area so as to draw locally then to shift the square QR without tilting it out of position. A protractor has a clutch which allows the square QR to be variably tilted to suitable positions for measuring and drawing. The pin indexed on the arm N311, may be made to bear against the straight line portion of the top edge of the straight edge 17a. The portion of the leg 16b that forms the tip of the arrow mark 162 or the outside center corner 16d of the square may be made to bear against one of the fixed points on the top edge of hinged straight edge 17a, located at the bottom of the board In, or a similar edge 17b at the side of the board. The arrow mark 160 and the outside center corner 16d act as indicator points and bearing points. The edges 17a and 1711 are hinged so that they may be raised above the surface of the board In to form a bearing surface with its edge to allow the pins on the pivot arms N3a and N3b to bear against it, to thus enable the draftsman to quickly and accurately adjust the drafting machine 16 to a selected tilted or horizontal position. When the tilting angle has been set, the machine 16 is pushed up on the board 1a and the straight edges are pivoted down to the positions shown by dot-dash outlines, so that they will not project above the working surface of the board 1a. This hinging of the edges 17a and 17b allows the scales of the square QR to project over the edge of the board 1a without them fouling the edges 17a and 17b when they are used in their areas. The leg 16b is longer than the distance from the outside corner 16d to the arrow mark 16e on the leg 16b. Thus this square dilfers in proportion to the arrangement for the square Q. The arrangement for leg 16a is similar to that shown for the square Q. The edges 17a and 17b are used only for the quick accurate setting of selective angles or tilting positions of the machine 16. The index arms N301 and N3b have protractors 13, but no clamping parts are needed. The drafting machine 16 with its protractor 160 may be used alone as an angular positioning means to set and hold the square QR at various angles, but it is not indexed to allow intermittent interchanging of the various odd angles, only 30, 45 and 90. Each time a new angle is used, it has to be reset accurately, which takes considerable time and effort. The protractor 160 is proportionately much smaller than the index arms N3a and N312, in allowing accurate setting of a desirable angle or tilt. The arrangement shown for leg 16b allows the use of small low weight index arm N311.

Both index arms and their supplementary parts may be omitted, or only one index arm such as arm N3a may be used.

FIGURE 16 shows a modified use of the square Q. A conventional drafting machine 18, which is similar to the machine 16, is hinged to the board 1b. A conventional protractor 18b on the machine 18 has a support 18a attached. This support 18a may be pivoted around the protractor 18b. A modified L-shaped square QL is made up of a square Q, with the leg extensions 19a and 19b. The square QL is used similar to the L-shaped square formed by scales 16a and 16b, as shown in FIG. 15. The square QL has an index arm N4, which is similar to index arm N1. The end pins are arranged the same as for square Q, to allow indexing of selected angles. The index arm N4 and the pins 5h and 5k may have protractor-clamps C1, C2 and C3 or the like to allow clamping of the square QL to the short straight edge portion of support 18a. This straight edge of support 18a works in a similar manner to the straight edge 17a. It allows the indexing of an angle, at the same time allowing the long legs of the square to project past the plane of the straight edge. Both legs of square QL may have hinges and pin arms to allow interchanging or additional clamps, and index arm to engage the straight edge on the support 18a. This square QL would be suitable for drawing long lines. This arrangement would enable the use of the short non-cumbersome index arm N4. The extension legs 19a and 1% may be made in various suitable lengths.

FIGURE 17 shows a modified graphic device which has an L-shaped square QS which is similar to the square Q. The legs 20a and 20b are conventional interchangeable drafting machine scales. The L-shaped center member 21 has grooves which fit the clips on the ends of .the legs 20a and 2.01). The index arms N5 and N6 are similar to index arm N1. The end pins 5m may be suitably attached to the member 2'1. Protractors and/or clamps may be used. The member :21 may have a carriage track and a carriage B.

The graphic L-shaped squares and the like that have been previously described may have modified pins similar to pin 5b, but longer so they may be made to project below the working plane to be drawn on. These modified long pins may be magnetized so they may act as magnetic clamps when they are made to bear against a metal edge with iron in it, particularly in the reverse bearing direction from that shown against the T-square 2 in FIG. 2. This arrangement would allow these graphic devices to be clamped onto a steel plate and the like, so as to use it to help mark layout lines on the plate and the like. Such long pins may also be made to bear against a piece of lumber, to allow the L-shaped square to be used to layout rafter cuts and the like.

Thus it will be seen that I have provided an economical and efiicient graphic equipment capable of performing a wide variety of operations to suit conditions.

While I have illustrated and described several embodiments of my invention, it will be understood that these are by way of illustration only, and that various changes and modifications may be made within the contemplation of my invention and within the scope of the following claims.

I claim:

1. A drafting instrument comprising an L-shaped square, scale means on said square, straight edge means in contacting relationship with said square, said square being mounted adjacent to a drawing area, and being tiltably mounted with respect to a straight portion of said straight edge means selectively about two bearing points spaced along an outer edge of one leg of said square, only one of said bearing points engaging said straight portion when the said square is tilted, said square having a straight indexing arm attached to said leg, said indexing arm having a pin means equidistantly spaced from said bearing points, said pin means being engageable with said straight portion, and adjustable means on the said indexing arm to selectively vary the angle between said square and said straight portion, said square being tiltable in opposite directions by selectively engaging the said bearing points and said pin means to obtain opposite sets of sloping positions for the legs of said square to allow the drawing of sets of lines ninety degress to each other and oppositely sloped, said pin means being retractable from said straight port-ion to allow both of said bearing points to engage said straight portion simultaneously to position the said square into a non-tilted position to permit nonsloping lines to be measured and drawn at right angles to each other along the edges of the said square, said straight edge means having an anchored portion secured to a fixed object adjacent to said drawing area, means interconnecting said anchored portion to said straight portion to automatically maintain said square in a predetermined angular position as said square is swept over the entire drawing area.

2. A drafting instrument as recited in claim 1 wherein said indexing arm is attached at two widely separate points on said leg, said indexing arm being kept clear of the adjacent outer edge of said leg, said scale means including graduations on said adjacent outer edge, thereby allowing scaling and drawing along said adjacent outer edge between said separate points while said indexing arm is attached to said leg.

3. A drafting instrument as recited in claim 1 wherein said adjustable means includes a threaded shaft, a nut engaged to said shaft and a pin holder, said pin means engaged with said holder, said nut being interconnected with said pin holder for selectively positioning said pin means laterally of said leg in response to rotation of said nut to obtain Vernier adjustment to said angular position.

4. A drafting instrument as recited in claim 3 wherein said adjustable means includes a plurality of nuts and pin holders at spaced points along said indexing arm each of said nuts being interconnected with one of said holders for selectively positioning said pin holders laterally of 15 said leg, said' pin means being engageable with said holders, whereby said square may be quickly moved and indexed to a plurality of angular positions with respect to said straight portion or in coincidence therewith.

5. A drafting instrument comprising an L-shaped square means, said square means including a scale means mounted adjacent the edges of said square means, said square means having an L-shaped track, said L-shaped track being formed by two intersecting straight track portions, a carriage mounted in said track, said, carriage having a rigid protruding portion extending outwardly over the inner edges of said square means when said carriage is positioned at the intersection of the legs of said square means, said protruding portion having an axis of forty-five degrees in a horizontal plane with respect to the longitudinal axes of said inner edges, amarking means positioned on said axis of said protruding portion so as to extend slightly outwardly from said inner edges and being engaged to and confined by said protruding portion so as to move with said carriage, angular positioning means to maintain said square means in a predetermined angular position as it is swept over a drawing area, said carriage being movable along said track to allow said marking means to be used to draw intersecting straight lines at right angles to each other, with minimum movement of said carriage, said scale means allowing scaling of the lengths of lines while drawing, whereby said instrument enables quick and accurate drawing of intersecting straight lines that are at right angles to each other, the drawing action being continuous and with minimum effort.

6. A drafting instrument as recited in claim wherein said marking means includes a single marker and wherein said marking means includes a control element pivotally mounted on said carriage and means responsive to the arcuate position of saidcontrol element for resetting the width of lines to be drawn with said single marker and wherein said control element being positioned so a draftsman may grip itcontinuously while drawing so as to manipulate it for lateral movement and pivotal movement, thereby allowing selective width lines to be drawn at right angles to each other at a rapid rate.

7. A drafting instrument as recited'in claim 5 wherein said scale means is mounted on said carriage.

8. A drafting instrument as recited in claim 5 wherein said angular positioning means includes a straight. edge, and-wherein said square means is tiltably mounted with respect, to said straight edge about two bearing points spaced along an outer edge of one leg of said square r means, only one of said bearing points engaging said straight edge when the said square means is tilted, said square means having a straight indexing arm attachedto said leg, said indexing arm having a pin equidistantly spaced from said bearing points, said pin engageable with r said straight edge and being adjustable on the indexing arm to vary the angle betweensaid square means and said straightedge for selectively tilting the said square means relative to the said straight edge, said square means being tiltable in opposite directions by selectively engaging the bearing points and said pin on said straight edge to obtainopposite sets of sloping positions for the legs of said square means to allow the drawing of sets of lines ninety degrees to each other and oppositely sloped, said-pin beingretractable from said straight edge to allow both of said bearing points to engage said straight edge simultaneously to position the said square means in a non-tilted position to permit non-sloping lines to be measured and drawn at rightangles toeach other alongsthe edges of the said square means.

9. A drafting instrument as recited in claim 5 wherein said angular positioning means is a conventional type drafting machine that sweeps over a drawing including a swivel arm of the parallelogram type having afixed end stationarily anchored adjacent said drawing area, a clutch at the other end of said arm and wherein said square means iscoupled to said clutch, together with fixed edge meansadjacent said drawing area, an indexing arm secured to one of said legs and being of variable effective length, two indicators along the said last mentioned leg, said indexing arm being midway between said indicators and engageable with said fixed edge means, whereby selective angles of tilt of said square means relative to said fixed edge means may be obtained quickly and accurately and may be maintained by engaging said clutch, thereby allowing said square means to be swept over said drawing area free of said fixed edge means, said square means being tiltable in one direction after engaging one of said indicators to said fixed edge means and engaging said indexing arm to said fixed edge means and being tiltable to an opposite direction after engaging the other of said indicators to said fixed edge means, whereby one setting of said indexing arm is used to tilt said square means in opposite directions.

10. A drafting instrument as recited in claim 5 wherein said marking means includes a control element mounted on said carriage for reciprocable movement toward and away from said drawing area, said marking means initiating marking said drawing area in response to a downward movement of said control element and said marking terminating in response to an upward movement of said control element, said control element being positioned so a draftsman may grip it continuously while drawing, whereby said marking meanscannot slip out of alignment with said square means when dotted lines are being drawn.

11. A drafting instrument as recited in claim 6 wherein said control element is mounted to allow movement towards and away from a drawing, said single marker initiating marking said drawing area in response to a downward movement of said control element and said marking terminating in response to an upward movement of said control element.

12. A drafting instrument as recited in claim 11 wherein said scale means is mounted on said carriage.

13. A drafting instrument comprising an L-shaped square, scale means on said square, said scale means including scaling graduations on thin, narrow flexible plastic strips that are positioned along at least one edge of each of the legs of said square, said plastic strips being removable and interchangeable with like graduated plastic strips having different graduations, straight edge means incontacting relationship with said square, said square being mounted adjacent to a drawing area, and being tiltably mounted with respect to a straight portion of said straight edge, means selectively about two bearing points spaced along an outer edge of one leg of said square, only one of said bearing points engaging said straight portion when the said squareis tilted, said square having a straight indexing arm attached to said leg, said indexing arm having a pin equidistantly spaced from said bearing points, said pin being engageable with said straight portion, and adjustable means on the said indexing arm to selectively vary the angle between said square and said straight portion, said square beingtiltable in opposite directions by selectively engaging the said bearing points and said pin to obtain opposite sets of sloping positions for the legs of said sqnareto allow the drawing of sets of lines ninety degrees to each other and oppositely sloped, said pin being retractable from said straight portion to allow both of said bearing points to engage said straight portion simultaneouslyto position the said square into a non-tilted position to permit non-sloping lines to be measured and drawn at right angles to each other along the edges of the said square, said straight edge means having an anchored portion secured to a fixed object adjacent to said drawing area, means interconnecting said anchored portion to said straight portion to automatically maintain said square in a predetermined angular position as said square is swept over the entire drawing area.

(References on following page) References Citefi in the file of this patent UNUSED STATES PATENTS Gillette Nov. 29, 1887 Blake Nov. 13, 1888 Norfolk Mar. 6, 1906 Schenk Apr. 1, 1913 Holmes June 10, 1913 Requa May 11, 1915 Allyn Oct. 12, 1915 10 18 For'tin June 28, 1927 Poulsen Oct. 2, 1934 8011611 June 23, 1953 Graham Apr. 21, 1959 FOREIGN PATENTS Germany June 21, 1909 Germany Dec. 12, 1921 Switzerland July 2, 1928 Switzerland Mar. 16, 1949 

1. A DRAFTING INSTRUMENT COMPRISING AN L-SHAPED SQUARE, SCALE MEANS ON SAID SQUARE, STRAIGHT EDGE MEANS IN CONTACTING RELATIONSHIP WITH SAID SQUARE, SAID SQUARE BEING MOUNTED ADJACENT TO A DRAWING AREA, AND BEING TILTABLY MOUNTED WITH RESPECT TO A STRAIGHT PORTION OF SAID STRAIGHT EDGE MEANS SELECTIVELY ABOUT TWO BEARING POINTS SPACED ALONG AN OUTER EDGE OF ONE LEG OF SAID SQUARE, ONLY ONE OF SAID BEARING POINTS ENGAGING SAID STRAIGHT PORTION WHEN THE SAID SQUARE IS TILTED, SAID SQUARE HAVING A STRAIGHT INDEXING ARM ATTACHED TO SAID LEG, SAID INDEXING ARM HAVING A PIN MEANS EQUIDISTANTLY SPACED FROM SAID BEARING POINTS, SAID PIN MEANS BEING ENGAGEABLE WITH SAID STRAIGHT PORTION, AND ADJUSTABLE MEANS ON THE SAID INDEXING ARM TO SELECTIVELY VARY THE ANGLE BETWEEN SAID SQUARE AND SAID STRAIGHT PORTION, SAID SQUARE BEING TILTABLE IN OPPOSITE DIRECTIONS BY SELECTIVELY ENGAGING THE SAID BEARING POINTS AND SAID PIN MEANS TO OBTAIN OPPOSITE SETS OF SLOPING POSITIONS FOR THE LEGS OF SAID SQUARE TO ALLOW THE DRAWING OF SETS OF LINES NINETY DEGRESS TO EACH OTHER AND OPPOSITELY SLOPED, SAID PIN MEANS BEING RETRACTABLE FROM SAID STRAIGHT PORTION TO ALLOW BOTH OF SAID BEARING POINTS TO ENGAGE SAID STRAIGHT PORTION SIMULTANEOUSLY TO POSITION THE SAID SQUARE INTO A NON-TILTED POSITION TO PERMIT NONSLOPING LINES TO BE MEASURED AND DRAWN AT RIGHT ANGLES TO EACH OTHER ALONG THE EDGES OF THE SAID SQUARE, SAID STRAIGHT EDGE MEANS HAVING AN ANCHORED PORTION SECURED TO A FIXED OBJECT ADJACENT TO SAID DRAWING AREA, MEANS INTERCONNECTING SAID ANCHORED PORTION TO SAID STRAIGHT PORTION TO AUTOMATICALLY MAINTAIN SAID SQUARE IN A PREDETERMINED ANGULAR POSITION AS SAID SQUARE IS SWEPT OVER THE ENTIRE DRAWING AREA. 